Monday, October 20, 2014

Nice fall weather this week

Temperatures will be running well above normal this week over southern Manitoba as an upper ridge of high pressure builds over the eastern Prairies. Sunny skies and gusty south winds Tuesday will send temperatures into the mid to upper teens, with lows 20s likely across SW Manitoba. On Wednesday, clouds will increase ahead of a weak system crossing southern Manitoba that may trigger some scattered showers by afternoon or evening. Temperatures however will remain mild in the mid to upper teens. Sunshine will return for Thursday and Friday with temperature again in the mid to upper teens, some 10C above normal for late October. Slightly cooler conditions are expected early next week, although there are no indications at this point of a change to a prolonged below normal temperature pattern through the end of October.

Rob a very interesting Blog discussing The imminent eruption of Bardarbunga icelands largest Volcano can be found at http://www.jonfr.com/volcano/?p=5191Comments include experts from IMO and elsewhere with links to GPS Data and Webcams and Earthquake monitors.BB has undergone two months of spewing out enormous quantities Of SO2 and other gasses as well as more Lava than anything since Laki 1783 BB 1862 and Askja 1875. and is on a pace to erase those records. Activity in the last 48 hours has changed remarkably.

Yesterdays most recent update of yhe Volcano sire Change the last digit to 4 ( p=5194) has started discussion of the SO2 increasing in the tropsphere and the long term impact on the mid latitudes weather. Lava is still flowing out at 100 m3/ sec about the amount flowing down the red River today past Drayton ND just a few miles from the canadian Border.

Seems more like a long term eruption than an explosive one Lots of speculation on the eventual outcome but the Holohuran Lava and gasses have started to pose some serious inconvenience at 35000 Tons of SO2 per day _by my calc about 2 million tons to date.Interesting update to the weather and climatic effect of this at http://onlinelibrary.wiley.com/doi/10.1029/2001JD002042/full

Anonymous.. No scary snowstorms or cold blasts expected for Halloween at this point! Current guidance is showing a ridge of high pressure moving across southern Manitoba for Friday, possibly with increasing southerly winds by evening depending on how quickly the ridge pushes east. That should mean dry weather for Halloween along with seasonable temperatures (around +5-7C or so during the day)

There likely will be some enhanced bands of lake effect precipitation off the south end of the lakes Tuesday, but instability looks marginal with only about -5C air at 850 mb moving over +7C lake water.. so streamers shouldn't be that heavy. Generally you need a lake-850 temperature difference of 13C or more for lake effect streamers (along with good wind alignment and some lift) and ideally 18C or more for more intense bands.

Halloween evening still looking dry with cool high pressure drifting across southern MB Friday. Daytime highs will likely be a little colder than normal, around +3C or so after a frosty start (early morning temps of -5C or so depending on cloud cover) Temperatures for Halloween evening likely around the freezing mark, with a bit of a southeast breeze. Not bad considering what it could be like at his time of year..

Chilly night ahead as cold high pressure builds over southern Manitoba with clear skies and diminishing winds. General guidance is for overnight lows in the -5 to -7C range for Winnipeg, except for the NAM which is way too warm at -3C. EC going for a low of -9C which is the coldest of all guidance. We'll see if we get that low.. it's possible although we get a bit of a light south flow off the city by early morning which may save the airport from bottoming out. Regardless, coldest night of the season so far on the way!

Sunny and chilly tomorrow with highs only near freezing to +2C, with an increasing south wind in the afternoon and evening which will put a nip in the air.. especially for the trick or treaters Friday evening. All in all though, a nice dry evening ahead for Halloween, not bad considering what it could be like at this time of year!

Current guidance hinting at two precip events in the next week or so.. one around Nov 3-4th, and another around the 7th. First system looks like mainly rain, but second system looks a bit colder, so some snow possible with that one. Both the Canadian GLB and American GFS models were showing a strong Dakota low on the 7th giving possible accumulating snow to southern MB, but Euro was further north and warmer.. and today's GFS was trending that way as well. Still a lot of uncertainty on these systems..

Things suddenly don't look so rosy down the road. Models are hinting at the potential of our 1st wintery blast later next week with the potential for a major snowfall but it's the cold blast come mid month that models are hinting at, that is kinda scary.

Right now.. it's looking like we may escape with some rain or wet snow Friday before the cold plunge on the weekend, but little in the way of accumulating snow over the weekend. But models have been inconsistent on the snow chances as we get into this colder weather, so we'll have to wait and see how the guidance trends this week.

Rob, do you know why the maximum visibility at the Calgary airport ( at 64 km ) is so much more than Winnipeg airport's maximum visibility ( at 24 km ) ?? I would think that the vast barren landscape of the Winnipeg airport under ideal conditions would be no different than Calgary airport. Do you know why there is a 40 km difference.??

It's because of the mountains. On flat ground, there's a limit as to how far you can see due to the curvature of the earth. Because of their height, the Rockies allow you a greater maximum visibility range since they can be seen above the curvature of the earth, provided the air is clear enough. That's why stations near mountain ranges can report greater visibilities than a standard airport site.

You're welcome. For really impressive visibility, see the obs from Mount Washington in New Hampshire (KMWN), elevation 6000 feet. On clear days, they report visibilities of 100 miles or more! Today for example, they went from 1/16 mile in fog to 100 miles in clear skies within an hour!

This also shows how elevation plays a role in reporting visibility. The higher you are, the greater the visibility range.

NAM, GFS and GLB all hinting that we may see our first coating of snow here in Winnipeg and the RRV Saturday night into early Sunday as a weak clipper tracks in from the northwest. Doesn't look like a lot.. perhaps 2-4 cm, but it should be enough to wake up to a white coating Sunday morning. Temps should be cold enough for it to stick around for a bit..

Nam has backed off on that snow for Saturday night.. with only a dusting noted now. Looks like impulse will be weaker than earlier shown, which agrees with drier canadian and European solutions. We'll see if that trend continues. Overall, looks like a lot of cold but not a lot of snow on the way over the weekend through next week, but it won't take much for even a minor system to give us some accumulating snow given the cold air coming.